Silicide processes have been widely used to form silicide formations for contacts on gate regions and source/drain (S/D) regions during the semiconductor device fabrication processing to improve the performance of the semiconductor device. The silicide formation improves the operational speed of the semiconductor device by reducing the contact resistance between the metal contact and the source and drain regions.
Silicide formation materials that have been employed with semiconductor structures include Al-silicide, Ni-silicide, Pt-silicide, Co-silicide, Cr-silicide, Ti-silicide, NiI-xPtx-silicide, W-silicide, Mo-silicide, Ag-silicide, Au-silicide, Ta-silicide, and Er-silicide.
Some silicide formations have been observed to pose a risk of leakage or shorting of a silicided S/D junction. The diffusion characteristics of unreacted metal into underlying doped silicon (Si), silicon germanium (SiGe) and germanium (Ge) substrates can create problems such as piping/spiking defects during the silicidation process. Such problems can lead to leakage of current into the channel as well as the junction regions, resulting in degradation in device performance.
Some silicide formations have been observed to be sensitive to oxygen contamination from the ambient air, wet etch chemistries and from residual interfacial contaminants such as native oxides. Such contamination can lead to rough and/or insulating interfaces causing high contact resistance in the device.